Merrifield Resin Supported Copper Catalyst for Asymmetric Cyclopropanation

Significance A recyclable Merrifield resin supported copper catalyst for asymmetric cyclopropanation of styrene was developed. Aza(bisoxazoline) ligand 1 was attached to the Merrifield resin and the resulting immobilized ligand 2 was evaluated in copper(I)-catalyzed asymmetric cyclopropanation. The cyclopropanation of styrene with ethyl diazoacetate by using Cu(OTf) 2 · 2 (1 mol%) gave the trans / cis isomers of the cyclopropanation products in a 74:26 ratio in 94% yield with 99% ee ( trans ) and 90% ee ( cis ), respectively. This supported catalyst was reused without loss of selectivity (see scheme).